Fabrication of CDMS Dark Matter Detector Using Bi-layer Lift-off Technique and Detection of Axions/Axion Like Particles (Alps) Using CsI(Tl) Scintillator Detectors

Abstract

Finding the nature of dark matter is one of the biggest quest in physics today. One of the various methods for dark matter detection is direct detection in which the interaction between dark matter and the normal matter is explored. The extremely weak nature of dark matter particles makes direct detection very challenging thereby demanding highly sensitive detectors. SuperCDMS experiment uses cryogenic superconducting Ge and Si as target materials with transition edge sensors (TES) for direct dark matter detection. The classic fabrication technique of CDMS detectors uses chemical etching of aluminum and tungsten thin films deposited on Si and Ge single-crystals to photolitho-graphically fabricate TESs on the detectors. In this work, I have explored another technique called the bi-layer lift-off process which allows the deposition of phonon absorbing aluminum layer di-rectly on the substrate, thereby improving the phonon-collection efficiency in the detectors and allowing for low threshold detection. It also allows us to explore other target materials like sap-phire, GaAs, diamond, SiC, etc. for sub-GeV dark matter and CEνNS searches. Results from a new sapphire detector are discussed. Null results so far for WIMP dark matter have resulted in increased interest in exploring other dark matter candidates i.e., axions or axion-like-particles (ALPs). Searches for pseudoscalar axion-like particles typically rely on their decay to photons in beam dumps or their conversion into photons in haloscopes and helioscopes. In this thesis, I present the preliminary results from the study of a 45 Kg prototype detector made out of thallium-induced cesium iodide CsI(Tl) scintillator carried out at a 1 MW TRIGA type nuclear reactor situated at the Nuclear Science Center (NSC) at Texas A&M University to search for ALPs which promises lower background using single scatter (veto) technique. Results from a scaled-up experiment consisting of a 30 kg fiducial mass of CsI(Tl) and the background analysis results and projected sensitivity for ALPs with photons, electrons, and nucleons are discussed. Close proximity to the core will have visibility to ALP decays and inverse Primakoff scattering inside the CsI(Tl) crystals, providing the world’s best laboratory-based constraints to the ALP-photon coupling over a wide sub-MeV ALP mass range.